This invention relates to optoelectric transducers, and more particularly to arrays of optoelectric transducers which may be fabricated in modular form for mounting on printed-circuit boards.
The need for bandwidth in communications systems has become acute due to the change of interpersonal communications from low-bandwidth audio to large-bandwidth video, and also by the increased high-speed traffic in large blocks of data, as for example in the downloading of audio and video files. Even overland microwave communications systems, which have bandwidths of tens and hundreds of megahertz (MHz), and which were in the past sufficient to handle hundreds or thousands of telephone calls are now obsolete, because of the large number of users of broadband communications. It is widely expected that optical communications paths will become the preferred medium for wideband communications in the future, because of the relatively low cost of optical fibers, their small size, which allows many paths to occupy a small space, and because of the potentially great bandwidth they can provide.
At present, most signal processing is performed by electronic devices, and very little processing is performed optically. Consequently, each location at which broadband signals are handled has one or more electronic equipments such as a computer or digital processor. Most often, these are assemblies including one or more printed-circuit boards, on which electrically conductive traces are defined by processes known generally as xe2x80x9cprinting,xe2x80x9d which provide reliable and repeatable formation of exceedingly minute and complex electrical circuits between or among various electrical devices, including digital processors of various sorts, but which may also include analog processing devices.
In the past, the designer or manufacturer of a printed-circuit board or electrical equipment which required an interface or interconnection to an optical signal path designed his own interface to the optical fiber, with the result that a communication equipment would sometimes have a plurality of optical fiber xe2x80x9cpigtailsxe2x80x9d to which other optical fibers could be connected. Such equipments are still in widespread use. The requirement for handling plural pigtails of optical fiber associated with a piece of equipment led to the design and adoption of xe2x80x9cribbonsxe2x80x9d of side-by-side optical fibers, which reduced the need for routing individual optical fibers by allowing a single ribbon cable to be routed. There was still a need for separating the optical fibers of the ribbon cable in order to make the connections of each optical fiber to its transducer, so the routing problem was not fully solved. An xe2x80x9cMT ferrulexe2x80x9d was designed by Nippon Telegraph and Telephone (NTT), which essentially consisted of a block encapsulating the end of an optical ribbon, polished and keyed to a pair of keying apertures into which keying pins could be inserted. This ferrule was found to be useful, as it eliminated the need to splay the fibers of the ribbon one from the other in order to make connection of one optical fiber ribbon to another.
Improved modular optoelectric transducers are desired.
A modular transducer according to the invention is intended for mounting onto an underlying printed-circuit board, for transducing between optical signals propagating through an MT ferrule and electrical signals. The modular transducer comprises an optoelectronic or optoelectric transducer solid-state device or integrated circuit including a planar optical interface surface and a plurality of optoelectric transducer elements arranged in a line array along an array axis with a pitch of 0.250 mm. The optoelectric transducer integrated circuit also includes at least one individual electrical connection for each of the optoelectric transducer elements and one electrical connection common to all of the optoelectric transducer elements. At least the one individual electrical connection for each of the optoelectric transducer elements is located on the planar optical interface surface. A heat spreading substrate which at least thermally conductive is included. The heat spreading substrate defines a front surface, which defines a planar portion and at least one depressed portion in which the optoelectric transducer integrated circuit lies, with the planar portion of the front surface of the heat spreading substrate substantially coplanar with the planar optical interface surface. The heat spreading substrate also defines a rear surface substantially parallel with the planar portion of the front surface. A transparent film extends over the planar optical interface circuit and at least a portion of the front surface of the heat spreading substrate. The transparent film bears electrically conductive circuit traces connected to the electrical connections of the optoelectric transducer elements. First and second alignment pins having diameters of 0.698 mm extend substantially perpendicularly from the planar portion of the front surface of the heat spreading substrate at locations lying substantially on the array axis at distances of 2.3 mm from the center of the line array.
The alignment pins extend through the transparent film if the transparent film overlies the intended or desired pin locations. A heat sink includes substantially mutually orthogonal first and second planar surfaces. At least a portion of the first planar surface of the heat sink is thermally coupled to the rear surface of the heat spreading substrate for heat transfer therebetween. An interface printed circuit includes a dielectric sheet defining first and second broad surfaces. The dielectric sheet is physically supported, at least in part, by the second surface of the heat sink. The interface printed circuit further includes electrically conductive circuit traces having electrical contact or coupling to at least some of the electrically conductive traces borne by the transparent film. The interface printed circuit further includes electrically conductive bond pads connecting to at least some of the electrically conductive traces of the interface printed circuit. The electrically conductive bond pads are generally planar connecting surfaces physically supported by the interface printed circuit dielectric sheet. The electrically conductive bond pads are accessible on the second broad surface of the dielectric sheet.
In one embodiment of the invention, the modular transducer further includes a protruding element projecting from the second side of the dielectric sheet, for engaging with a corresponding aperture of the underlying printed circuit for at least registering the bond pads with corresponding pads of the underlying printed circuit board.
In another avatar of the invention, the modular transducer further comprises an optoelectric driver integrated circuit including an electrical connection surface, the optoelectric driver integrated circuit being supported by the heat spreading substrate with the electrical connection surface coplanar with the planar portion of the front surface of the heat spreading substrate. At least some electrical connections of the electrical connection surface of the optoelectric driver integrated circuit are electrically connected to electrically conductive traces borne by the transparent film.
In a particularly advantageous manifestation of the invention, the modular transducer further includes an optical snout capable of accepting one of MTP, MPO, and MPX connector interfaces containing a MT ferrule, and optically mating the MT ferrule to the optoelectric transducer integrated circuit when the registration apertures of the MT ferrule are mated to the first and second alignment pins.